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  • 1.
    Fletcher, C. L.
    et al.
    Florida Inst Technol, Dept Phys & Space Sci, Melbourne, FL 32904 USA.
    Petit, V.
    Univ Delaware, Bartol Res Inst, Dept Phys & Astron, Newark, DE 19716 USA.
    Naze, Y.
    Univ Liege, FNRS GAPHE, STAR, Inst Astrophys & Geophys B5C, Allee 6 Aout 19c, B-4000 Liege, Belgium.
    Wade, G. A.
    Royal Mil Coll Canada, Dept Phys, POB 17000 Stn Forces, Kingston, ON K7K 0C6, Canada.
    Townsend, R. H.
    Univ Wisconsin, Dept Astron, 5534 Sterling Hall,475 N Charter St, Madison, WI 53706 USA.
    Owocki, S. P.
    Univ Delaware, Bartol Res Inst, Dept Phys & Astron, Newark, DE 19716 USA.
    Cohen, D. H.
    Swarthmore Coll, Dept Phys & Astron, 500 Coll Ave, Swarthmore, PA 19081 USA.
    David-Uraz, A.
    Univ Delaware, Bartol Res Inst, Dept Phys & Astron, Newark, DE 19716 USA.
    Shultz, Matthew
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Investigating the Magnetospheres of Rapidly Rotating B-type Stars2017In: Lives And Death-Throes Of Massive Stars / [ed] Eldridge, JJ; Bray, JC; McClelland, LAS; Xiao, L, 2017, no S329, p. 369-372Conference paper (Refereed)
    Abstract [en]

    Recent spectropolarimetric surveys of bright, hot stars have found that similar to 10% of OB-type stars contain strong (mostly dipolar) surface magnetic fields (similar to kG). The prominent paradigm describing the interaction between the stellar winds and the surface magnetic field is the magnetically confined wind shock (MCWS) model. In this model, the stellar wind plasma is forced to move along the closed field loops of the magnetic field, colliding at the magnetic equator, and creating a shock. As the shocked material cools radiatively it will emit X-rays. Therefore, X-ray spectroscopy is a key tool in detecting and characterizing the hot wind material confined by the magnetic fields of these stars. Some B-type stars are found to have very short rotational periods. The effects of the rapid rotation on the X-ray production within the magnetosphere have yet to be explored in detail. The added centrifugal force due to rapid rotation is predicted to cause faster wind outflows along the field lines, leading to higher shock temperatures and harder X-rays. However, this is not observed in all rapidly rotating magnetic B-type stars. In order to address this from a theoretical point of view, we use the X-ray Analytical Dynamical Magnetosphere (XADM) model, originally developed for slow rotators, with an implementation of new rapid rotational physics. Using X-ray spectroscopy from ESA's XMM-Newton space telescope, we observed 5 rapidly rotating B-types stars to add to the previous list of observations. Comparing the observed X-ray luminosity and hardness ratio to that predicted by the XADM allows us to determine the role the added centrifugal force plays in the magnetospheric X-ray emission of these stars.

  • 2.
    Kochukhov, Oleg
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Shultz, Matthew
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Univ Delaware, Dept Phys & Astron, Newark, DE 19711 USA.
    Neiner, C.
    Univ Paris Diderot, Sorbonne Univ, Sorbonne Paris Cite, LESIA,Observ Paris,PSL Res Univ,CNRS, 5 Pl Jules Janssen, F-92195 Meudon, France.
    Magnetic field topologies of the bright, weak-field Ap stars θ Aurigae and ε Ursae Majoris2019In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 621, p. 1-18, article id A47Article in journal (Refereed)
    Abstract [en]

    Context. The brightest magnetic chemically peculiar stars theta Aur and epsilon UMa were targeted by numerous studies of their photometric and spectroscopic variability. Detailed maps of chemical abundance spots were repeatedly derived for both stars. However, owing to the weakness of their surface magnetic fields, very little information on the magnetic field geometries of these stars is available.

    Aims. In this study we aim to determine detailed magnetic field topologies of theta Aur and epsilon UMa based on modern, high-resolution spectropolarimetric observations.

    Methods. Both targets were observed in all four Stokes parameters using the Narval and ESPaDOnS spectropolarimeters. A multi-line technique of least-squares deconvolution was employed to detect polarisation signatures in spectral lines. These signatures were modelled with a Zeeman-Doppler imaging code.

    Results. We succeed in detecting variable circular and linear polarisation signatures for theta Aur. Only circular polarisation was detected for epsilon UMa. We obtain new sets of high-precision longitudinal magnetic field measurements using mean circular polarisation metal line profiles as well as hydrogen line cores, which are consistent with historical data. Magnetic inversions revealed distorted dipolar geometries in both stars. The Fe and Cr abundance distributions, reconstructed simultaneously with magnetic mapping, do not show a clear correlation with the local magnetic field properties, with the exception of a relative element underabundance in the horizontal field regions along the magnetic equators.

    Conclusions. Our study provides the first ever detailed surface magnetic field maps for broad-line, weak-field chemically peculiar stars, showing that their field topologies are qualitatively similar to those found in stronger field stars. The Fe and Cr chemical abundance maps reconstructed for theta Aur and epsilon UMa are at odds with the predictions of current theoretical atomic diffusion calculations.

  • 3.
    Mikulasek, Z.
    et al.
    Masaryk Univ, Brno, Czech Republic..
    Krticka, J.
    Masaryk Univ, Brno, Czech Republic..
    Janik, J.
    Masaryk Univ, Brno, Czech Republic..
    Henry, G. W.
    Tennessee State Univ, Nashville, TN 37203 USA..
    Zejda, M.
    Masaryk Univ, Brno, Czech Republic..
    Shultz, Matthew
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Paunzen, E.
    Masaryk Univ, Brno, Czech Republic..
    Jagelka, M.
    Masaryk Univ, Brno, Czech Republic..
    On the Nature of Rotation Period Variability of Magnetic Stars2017In: Stars: From Collapse To Collapse / [ed] Balega, YY Kudryavtsev, DO Romanyuk, II Yakunin, IA, 2017, Vol. 510, p. 220-223Conference paper (Refereed)
    Abstract [en]

    The magnetic chemically peculiar (mCP) stars of the upper main sequence exhibit periodic light, magnetic, radio, and spectroscopic variations that can be adequately explained by a model of a rigidly rotating magnetized star with persistent surface structures. The majority of mCP stars rotate at strictly constant periods. However, there are a few mCP stars whose rotation periods vary on timescales of decades while the shape of their phase curves remains unchanged. In the case of CU Vir and V901 Ori, we have detected cyclic period variations. We demonstrate that the period oscillations of CU Vir may be a consequence of the interaction of the internal magnetic field and differential rotation.

  • 4.
    Mikulasek, Z.
    et al.
    Masaryk Univ, Dept Theoret Phys & Astrophys, Brno, Czech Republic.
    Krticka, J.
    Masaryk Univ, Dept Theoret Phys & Astrophys, Brno, Czech Republic.
    Paunzen, E.
    Masaryk Univ, Dept Theoret Phys & Astrophys, Brno, Czech Republic.
    Svanda, M.
    Charles Univ Prague, Astron Inst, Prague, Czech Republic.
    Hummerich, S.
    Bundesdeutsch Arbeitsgemeinschaft Veranderliche S, Berlin, Germany.
    Bernhard, K.
    Bundesdeutsch Arbeitsgemeinschaft Veranderliche S, Berlin, Germany.
    Jagelka, M.
    Masaryk Univ, Dept Theoret Phys & Astrophys, Brno, Czech Republic.
    Janik, J.
    Masaryk Univ, Dept Theoret Phys & Astrophys, Brno, Czech Republic.
    Henry, G. W.
    Tennessee State Univ, Ctr Excellence Informat Syst, Nashville, TN 37203 USA.
    Shultz, Matthew
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Differential rotation in magnetic chemically peculiar stars2018In: CONTRIBUTIONS OF THE ASTRONOMICAL OBSERVATORY SKALNATE PLESO, ISSN 1335-1842, Vol. 48, no 1, p. 203-207Article in journal (Refereed)
    Abstract [en]

    Magnetic chemically peculiar (mCP) stars constitute about 10% of upper-main-sequence stars and are characterized by strong magnetic fields and abnormal photospheric abundances of some chemical elements. Most of them exhibit strictly periodic light, magnetic, radio, and spectral variations that can be fully explained by a rigidly rotating main-sequence star with persistent surface structures and a stable global magnetic field. Long-term observations of the phase curves of these variations enable us to investigate possible surface differential rotation with unprecedented accuracy and reliability. The analysis of the phase curves in the best-observed mCP stars indicates that the location and the contrast of photometric and spectroscopic spots as well as the geometry of the magnetic field remain constant for at least many decades. The strict periodicity of mCP variables supports the concept that the outer layers of upper-main-sequence stars do not rotate differentially. However, there is a small, inhomogeneous group consisting of a few mCP stars whose rotation periods vary on timescales of decades. The period oscillations may reflect real changes in the angular velocity of outer layers of the stars which are anchored by their global magnetic fields. In CU Vir, V901 On, and perhaps BS Cir, the rotational period variation indicates the presence of vertical differential rotation; however, its exact nature has remained elusive until now. The incidence of mCP stars with variable rotational periods is currently investigated using a sample of fifty newly identified Kepler mCP stars.

  • 5.
    Shultz, Matthew E.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Queens Univ, Dept Phys Engn Phys & Astron, Kingston, ON K7L 3N6, Canada.;Royal Mil Coll Canada, Dept Phys, Kingston, ON K7K 7B4, Canada.;ESO European Org Astron Res Southern Hemisphere, Casilla 19001, Santiago 19, Chile..
    Wade, G. A.
    Royal Mil Coll Canada, Dept Phys, Kingston, ON K7K 7B4, Canada..
    Rivinius, Th.
    ESO European Org Astron Res Southern Hemisphere, Casilla 19001, Santiago 19, Chile..
    Neiner, C.
    Univ Paris Diderot, UPMC Univ Paris 06, Sorbonne Univ,Observ Paris, PSL Res Univ,CNRS,LESIA,Sorbonne Paris Cite, 5 Pl Jules Janssen, F-92195 Meudon, France..
    Alecian, E.
    Univ Paris Diderot, UPMC Univ Paris 06, Sorbonne Univ,Observ Paris, PSL Res Univ,CNRS,LESIA,Sorbonne Paris Cite, 5 Pl Jules Janssen, F-92195 Meudon, France..
    Bohlender, D.
    Natl Res Council Canada, Herzberg Inst Astron & Astrophys, 5071 West Saanich Rd, Victoria, BC V9E 2E7, Canada..
    Monin, D.
    Natl Res Council Canada, Herzberg Inst Astron & Astrophys, 5071 West Saanich Rd, Victoria, BC V9E 2E7, Canada..
    Sikora, J.
    Queens Univ, Dept Phys Engn Phys & Astron, Kingston, ON K7L 3N6, Canada.;Royal Mil Coll Canada, Dept Phys, Kingston, ON K7K 7B4, Canada..
    The magnetic early B-type stars I: magnetometry and rotation2018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 475, no 4, p. 5144-5178Article in journal (Refereed)
    Abstract [en]

    The rotational and magnetic properties of many magnetic hot stars are poorly characterized, therefore the Magnetism in Massive Stars and Binarity and Magnetic Interactions in various classes of Stars collaborations have collected extensive high-dispersion spectropo-larimetric data sets of these targets. We present longitudinal magnetic field measurements < B-z > for 52 early B-type stars (B5-B0), with which we attempt to determine their rotational periods P-rot. Supplemented with high-resolution spectroscopy, low-resolution Dominion As-trophysical Observatory circular spectropolarimetry, and archival Hipparcos photometry, we determined P-rot for 10 stars, leaving only five stars for which P-rot could not be determined. Rotational ephemerides for 14 stars were refined via comparison of new to historical magnetic measurements. The distribution of P-rot is very similar to that observed for the cooler Ap/Bp stars. We also measured v sin i and v(mac) for all stars. Comparison to non-magnetic stars shows that v sin i is much lower for magnetic stars, an expected consequence of magnetic braking. We also find evidence that v(mac) is lower for magnetic stars. Least-squares deconvolution profiles extracted using single-element masks revealed widespread, systematic discrepancies in < B-z > between different elements: this effect is apparent only for chemically peculiar stars, suggesting it is a consequence of chemical spots. Sinusoidal fits to H line < B-z > measurements (which should be minimally affected by chemical spots), yielded evidence of surface magnetic fields more complex than simple dipoles in six stars for which this has not previously been reported; however, in all six cases, the second- and third-order amplitudes are small relative to the first-order (dipolar) amplitudes.

  • 6.
    Shultz, Matthew
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Kochukhov, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Wade, G A
    Rivinius, Th
    The pulsationally modulated radial crossover signature of the slowly rotating magnetic B-type star xi(1) CMa2018In: Monthly Notices of the Royal Astronomical Society: Letters, ISSN 1745-3925, Vol. 478, no 1, p. L39-L43Article in journal (Refereed)
    Abstract [en]

    We report the latest set of spectropolarimetric observations of the magnetic beta Cep star xi 1 CMa. The new observations confirm the long-period model of Shultz et al. (2017), who proposed a rotational period of about 30 years and predicted that in 2018 the star should pass through a magnetic null. In perfect agreement with this projection, all longitudinal magnetic field < B-z > measurements are close to 0 G. Remarkably, individual Stokes V profiles all display a crossover signature, which is consistent with < B-z > similar to 0 but is not expected when v sin i similar to 0. The crossover signatures furthermore exhibit pulsationally modulated amplitude and sign variations. We show that these unexpected phenomena can all be explained by a 'radial crossover' effect related to the star's radial pulsations, together with an important deviation of the global field topology from a purely dipolar structure, that we explore via a dipole+ quadrupole configuration as the simplest non-dipolar field.

  • 7.
    Shultz, Matthew
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. Univ Delaware, Dept Phys & Astron, 217 Sharp Lab, Newark, DE 19716 USA.
    Le Bouquin, J. -B
    Rivinius, Th.
    ESO European Org Astron Res Southern Hemisphere, Casilla 19001, Santiago 19, Chile.
    Wade, G. A.
    Royal Mil Coll Canada, Dept Phys & Space Sci, Kingston, ON K7K 7B4, Canada.
    Kochukhov, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Alecian, E.
    Univ Grenoble Alpes, IPAG, F-38000 Grenoble, France.
    Petit, V.
    Univ Delaware, Dept Phys & Astron, 217 Sharp Lab, Newark, DE 19716 USA.
    Pfuhl, O.
    Max Planck Inst Extraterr Phys, Giessenbachstr 1, D-85748 Garching, Bayern, Germany.
    Karl, M.
    Max Planck Inst Extraterr Phys, Giessenbachstr 1, D-85748 Garching, Bayern, Germany.
    Gao, F.
    Max Planck Inst Extraterr Phys, Giessenbachstr 1, D-85748 Garching, Bayern, Germany.
    Grellmann, R.
    Univ Cologne, Phys Inst, Zulpicher Str 77, D-50397 Cologne, Germany.
    Lin, C. -C
    Garcia, P.
    Univ Grenoble Alpes, IPAG, F-38000 Grenoble, France;Univ Lisbon, IST, Ctr Astrofis & Gravitacao, P-1049001 Lisbon, Portugal;Univ Porto, Fac Engn, Rua Dr Roberto Frias, P-4200465 Porto, Portugal.
    Lacour, S.
    CNRS, IPAG, F-38000 Grenoble, France.
    NU Ori: a hierarchical triple system with a strongly magnetic B-type star2019In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 482, no 3, p. 3950-3965Article in journal (Refereed)
    Abstract [en]

    NU Ori is a massive spectroscopic and visual binary in the Orion Nebula Cluster, with four components: Aa, Ab, B, and C. The B0.5 primary (Aa) is one of the most massive B-type stars reported to host a magnetic field. We report the detection of a spectroscopic contribution from the C component in high-resolution ESPaDOnS spectra, which is also detected in a Very Large Telescope Interferometer data set. Radial velocity (RV) measurements of the inner binary (designated Aab) yield an orbital period of 14.3027(7) d. The orbit of the third component (designated C) was constrained using both RVs and interferometry. We find C to be on a mildly eccentric 476(1) d orbit. Thanks to spectral disentangling of mean line profiles obtained via least-squares deconvolution, we show that the Zeeman Stokes V signature is clearly associated with C, rather than Aa as previously assumed. The physical parameters of the stars were constrained using both orbital and evolutionary models, yielding M-Aa = 14.9 +/- 0.5 M-circle dot, M-Ab = 3.9 +/- 0.7 M-circle dot, and M-C = 7.8 +/- 0.7 M-circle dot. The rotational period obtained from longitudinal magnetic field (B-z) measurements is P-rot = 1.09468(7)d, consistent with previous results. Modelling of (B-z) indicates a surface dipole magnetic field strength of similar to 8 kG. NU Ori C has a magnetic field strength, rotational velocity, and luminosity similar to many other stars exhibiting magnetospheric Ha emission, and we find marginal evidence of emission at the expected level (similar to 1 per cent of the continuum).

  • 8.
    Shultz, Matthew
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Rivinius, Th.
    ESO European Org Astron Res Southern Hemisphere, Casilla 19001, Santiago 19, Chile.
    Wade, G. A.
    Royal Mil Coll Canada, Dept Phys, Kingston, ON K7K 7B4, Canada.
    Alecian, E.
    Univ Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France.
    Kochukhov, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    HD 156324: A Tidally Locked Magnetic SB3 With an Orbitally Disrupted Centrifugal Magnetosphere2018In: CONTRIBUTIONS OF THE ASTRONOMICAL OBSERVATORY SKALNATE PLESO, ISSN 1335-1842, Vol. 48, no 1, p. 298-299Article in journal (Refereed)
    Abstract [en]

    Period analysis of radial velocity, equivalent width, and magnetic measurements of the SB3 system HD 156324 yield identical results in all cases, indicating the system is tidally locked with orbital and rotational periods of 1.58 d. Its H alpha emission profile exhibits marked morphological departures from the usual pattern observed amongst magnetic B-type stars, which can plausibly be ascribed to tidal disruption of the gravitocentrifugal potential.

  • 9.
    Shultz, Matthew
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Rivinius, Th.
    ESO European Org Astron Res Southern Hemisphere, Casilla 19001, Santiago 19, Chile.
    Wade, G. A.
    Royal Mil Coll Canada, Dept Phys, Kingston, ON K7K 7B4, Canada.
    Alecian, E.
    Univ Grenoble Alpes, IPAG, F-38000 Grenoble, France;CNRS, IPAG, F-38000 Grenoble, France;Univ Paris Diderot, UPMC, CNRS, LESIA,Observ Paris,UMR 8109, 5 Pl Jules Janssen, F-92190 Meudon, France.
    Petit, V.
    Univ Delaware, Dept Phys & Astron, Sharp Lab 217, Newark, DE 19716 USA.
    HD 156324: a tidally locked magnetic triple spectroscopic binary with a disrupted magnetosphere2018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 475, no 1, p. 839-852Article in journal (Refereed)
    Abstract [en]

    HD 156324 is an SB3 (B2VIB5VIB5V) system in the Sco OB4 association. The He-strong primary possesses both a strong magnetic field and Ha emission believed to originate in its centrifugal magnetosphere. We analyse a large spectroscopic and high-resolution spectropolarimetric data set. The radial velocities (RVs) indicate that the system is composed of two subsystems, which we designate A and B. Period analysis of the RVs of the three components yields orbital periods P-orb = 1.5806(1) d for the Aa and Ab components, and P-orb = 6.67(2) d for the B component, a PGa star. Period analysis of the longitudinal magnetic field (B,) and H alpha equivalent widths, which should both be sensitive to the rotational period Prot of the magnetic Aa component, both yield 1.58 d. Since P-orb = P-rot Aa and Ab must be tidally locked. Consistent with this, the orbit is circularized, and the rotational and orbital inclinations are identical within uncertainty, as are the semimajor axis and the Kepler corotation radius. The star's Ha emission morphology differs markedly from both theoretical and observational expectations in that there is only one, rather than two, emission peaks. We propose that this unusual morphology may be a consequence of modification of the gravitocentrifugal potential by the presence of the close stellar companion. We also obtain upper limits on the magnetic dipole strength B-d for the Ab and B components, respectively, finding B-d < 2.6 and <0.7 kG.

  • 10.
    Shultz, Matthew
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. Queens Univ, Dept Phys Engn Phys & Astron, Canada.;Royal Mil Coll Canada, Dept Phys, Canada..
    Wade, G. A.
    Royal Mil Coll Canada, Dept Phys, POB 17000 Stn Forces, Kingston, ON K7K 0C6, Canada..
    Confirming the oblique rotator model for the extremely slowly rotating O8f?p star HD 1082017In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 468, no 4, p. 3985-3992Article in journal (Refereed)
    Abstract [en]

    The O8f?p star HD 108 is implied to have experienced the most extreme rotational braking of any magnetic, massive star, with a rotational period P-rot of at least 55 yr, but the upper limit on its spin-down time-scale is over twice the age estimated from the Hertzsprung-Russell diagram. HD 108's observed X-ray luminosity is also much higher than predicted by the X-ray Analytical Dynamical Magnetosphere (XADM) model, a unique discrepancy amongst magnetic O-type stars. Previously reported magnetic data cover only a small fraction (similar to 3.5 per cent) of P-rot, and were furthermore acquired when the star was in a photometric and spectroscopic 'low state' at which the longitudinal magnetic field < B-z > was likely at a minimum. We have obtained a new ESPaDOnS magnetic measurement of HD 108, 6 yr after the last reported measurement. The star is returning to a spectroscopic high state, although its emission lines are still below their maximum observed strength, consistent with the proposed 55-yr period. We measured < B-z > = -325 +/- 45 G, twice the strength of the 2007-2009 observations, raising the lower limit of the dipole surface magnetic field strength to B-d >= 1 kG. The simultaneous increase in < B-z > and emission strength is consistent with the oblique rotator model. Extrapolation of the < B-z > maximum via comparison of HD 108's spectroscopic and magnetic data with the similar Of?p star HD 191612 suggests that B-d > 2 kG, yielding t(S,max) < 3 Myr, compatible with the stellar age. These results also yield a better agreement between the observed X-ray luminosity and that predicted by the XADM model.

  • 11.
    Shultz, Matthew
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. Queens Univ, Dept Phys Engn Phys & Astron, Kingston, ON K7L 3N6, Canada.;Royal Mil Coll Canada, Dept Phys, Kingston, ON K7K 7B4, Canada.;ESO European Org Astron Res Southern Hemisphere, Casilla 19001, Santiago 19, Chile..
    Wade, G. A.
    Royal Mil Coll Canada, Dept Phys, Kingston, ON K7K 7B4, Canada..
    Rivinius, Th.
    ESO European Org Astron Res Southern Hemisphere, Casilla 19001, Santiago 19, Chile..
    Neiner, C.
    Univ Paris Diderot, UPMC Univ Paris 06, Sorbonne Paris Cite, PSL Res Univ,CNRS,Sorbonne Univ,LESIA,Observ Pari, 5 Pl Jules Janssen, F-92195 Meudon, France..
    Henrichs, H.
    Univ Amsterdam, Astron Inst Anton Pannekoek, Sci Pk 904, NL-1098 XH Amsterdam, Netherlands.;Radboud Univ Nijmegen, Dept Astrophys, IMAPP, POB 9010, NL-6500 GL Nijmegen, Netherlands..
    Marcolino, W.
    Univ Fed Rio de Janeiro, Observ Valongo, Ladeira Pedro AntUnio 43, BR-20080090 Rio De Janeiro, Brazil..
    The pulsating magnetosphere of the extremely slowly rotating magnetic beta Cep star xi(1) CMa2017In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 471, no 2, p. 2286-2310Article in journal (Refereed)
    Abstract [en]

    xi(1) CMa is a monoperiodically pulsating, magnetic beta Cep star with magnetospheric X-ray emission that, uniquely amongst magnetic stars, is clearly modulated with the star's pulsation period. The rotational period P-rot has yet to be identified, with multiple competing claims in the literature. We present an analysis of a large ESPaDOnS data set with a 9 yr baseline. The longitudinal magnetic field < B-z > shows a significant annual variation, suggesting that Prot is at least of the order of decades. The possibility that the star's Ha emission originates around a classical Be companion star is explored and rejected based upon Very Large Telescope Interferometer AMBER and PIONIER interferometry, indicating that the emission must instead originate in the star's magnetosphere and should therefore also be modulated with Prot. Period analysis of Ha equivalent widths measured from ESPaDOnS and CORALIE spectra indicates P-rot > 30 yr. All evidence thus supports that xi(1) CMa is a very slowly rotating magnetic star hosting a dynamical magnetosphere. Ha also shows evidence for modulation with the pulsation period, a phenomenon that we show cannot be explained by variability of the underlying photospheric line profile, i.e. it may reflect changes in the quantity and distribution of magnetically confined plasma in the circumstellar environment. In comparison to other magnetic stars with similar stellar properties, xi(1) CMa is by far the most slowly rotating magnetic B-type star, is the only slowly rotating B-type star with a magnetosphere detectable in Ha ( and thus, the coolest star with an optically detectable dynamical magnetosphere), and is the only known early-type magnetic star with Ha emission modulated by both pulsation and rotation.

  • 12.
    Shultz, Matthew
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Wade, G. A.
    Royal Mil Coll Canada, Dept Phys, Kingston, ON K7K 7B4, Canada.
    Rivinius, Th.
    European Southern Observ, Casilla 19001, Santiago 19, Chile.
    Neiner, C.
    Univ Paris Diderot, UPMC Univ Paris 06, Sorbonne Univ, PSL Res Univ,CNRS,Observ Paris,LESIA,Sorbonne Par, 5 Pl Jules Janssen, F-92195 Meudon, France.
    Kochukhov, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Alecian, E.
    Univ Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France.
    Rotation, Emission, & Evolution of the Magnetic Early B-type Stars2018In: CONTRIBUTIONS OF THE ASTRONOMICAL OBSERVATORY SKALNATE PLESO, ISSN 1335-1842, Vol. 48, no 1, p. 175-179Article in journal (Refereed)
    Abstract [en]

    We report the results of the first population study of 51 magnetic early B-type stars, based upon a large database of high-resolution spectropolarimetry assembled by the MiMeS and BinaMIcS collaborations. Utilizing these data, rotational periods were determined for all but 5 of the sample stars. This enabled us to determine dipole oblique rotator model parameters, rotational parameters, and magnetospheric parameters. We find that the ratio of the Alfven radius to the Kepler corotation radius is highly predictive of whether or not a star displays Ha emission from a Centrifugal Magnetosphere (CM), as expected from theoretical considerations. We also find that CM host stars are systematically younger than the general population, as expected given that CM emission requires rapid rotation and a strong magnetic field, and a strong magnetic field will lead to rapid magnetic braking. We conclude that emission-line magnetic early B-type stars are, almost without exception, strongly magnetized, rapidly rotating, and young.

  • 13.
    Shultz, Matthew
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Wade, Gregg
    Royal Mil Coll Canada, Dept Phys, Kingston, ON K7K 7B4, Canada.
    Rivinius, Thomas
    ESO European Org Astron Res Southern Hemisphere, Casilla 19001, Santiago 19, Chile.
    Neiner, Coralie
    UPMC Univ Paris 06, Univ Paris Diderot, PSL Res Univ, LESIA,Observ Paris,CNRS,Sorbonne Univ,Sorbonne Pa, 5 Pl Jules Janssen, F-92195 Meudon, France.
    Alecian, Evelyne
    Univ Grenoble Alpes, IPAG, F-38000 Grenoble, France;CNRS, IPAG, F-38000 Grenoble, France;UPMC, Univ Paris Diderot, CNRS UMR 8109, LESIA,Observ Paris, 5 Pl Jules Janssen, F-92190 Meudon, France.
    Petit, Veronique
    Univ Delaware, Dept Phys & Astron, 217 Sharp Lab, Newark, DE 19716 USA.
    Grunhut, Jason
    Univ Toronto, Dunlap Inst Astron & Astrophys, 50 St George St, Toronto, ON M5S 3H4, Canada.
    What can magnetic early B-type stars tell us about early B-type stars in general?2017In: Lives And Death-Throes Of Massive Stars / [ed] Eldridge, JJ; Bray, JC; McClelland, LAS; Xiao, L, 2017, no S329, p. 126-130Conference paper (Refereed)
    Abstract [en]

    Some magnetic early B-type stars display H alpha emission originating in their Centrifugal Magnetospheres (CMs). To determine the rotational and magnetic properties necessary for the onset of emission, we analyzed a large spectropolarimetric dataset for a sample of 51 B5-B0 magnetic stars. New rotational periods were found for 15 stars. We determined physical parameters, dipolar magnetic field strengths, magnetospheric parameters, and magnetic braking timescales. H alpha-bright stars are more rapidly rotating, more strongly magnetized, and younger than the overall population. We use the high sensitivity of magnetic braking to the mass-loss rate to test the predictions of Vink et al. (2001) and Krti. cka (2014) by comparing ages t to maximum spindown ages t(S, max). For stars with M-* < 10 M-circle dot this comparison favours the Krti. cka recipe. For the most massive stars, both prescriptions yield t << t(S, max), a discrepancy which is difficult to explain via incorrect mass-loss rates alone.

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